基于RISE反馈的串联弹性驱动器最优控制方法

Optimal Control for Series Elastic Actuator Using RISE Feedback

串联弹性驱动器(Series elastic actuator, SEA)是机器人交互系统中的一种理想力源.本文针对非线性SEA的力矩控制问题提出一种基于RISE (Robust integral of the sign of the error)反馈的最优控制方法,能够克服模型参数不确定和有界扰动,实现SEA输出力矩在交互过程中快速平稳地收敛到期望值.具体来说,首先对SEA的模型进行分析和变换;然后假设模型参数和扰动均已知,并在此基础上基于二次型指标设计最优控制律;之后基于RISE反馈重新设计控制律抵消模型参数不确定性和有界扰动,基于Lyapunov理论分析控制器的收敛性和信号的有界性,实验结果表明这种基于RISE反馈的最优控制方法具有良好的控制性能和对有界扰动的鲁棒性.

Series elastic actuator (SEA)is an ideal power source in robots interaction systems.Aiming at SEA torque control,an optimization scheme with an RISE (robust integral of the sign of the error)feedback structure is proposed to ensure the output of SEA asymptotically tracks a desired time-varying torque despite uncertainties in the dynamics like bounded disturbance or parametric uncertainty.Specifically,the generic dynamics of SEA system is described and some analysis and transformation operations are performed.The system in which all terms are assumed to be known is feedback linearized and a control law is developed using the optimization method for a given quadratic performance index.Then the control law is modified to contain the RISE feedback term for identifying the uncertainty.At last,a Lyapunov stability analysis is included to show that the tracking error converges to zero with all signals bounded.Experiment results show that the suggested controller achieves satisfactory control performance and strong robustness to disturbance.